Rheostat



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Patented May 6, 1924.

UNITED STATES lPATENT OFFICE.

JOHN C. BOYTON, F CLEVELAND, AND HERBERT A. STEVENSON, OF LAKEWOOD,OHIO.

BHFDBTAT.

Application Med Iay 8,

To all whom it may concern.'

Be it known that we, (1) JOHN C. BeY- ToN, (2) HERBERT A. STEvENsoN,citizens of the United States, residing at (1) Cleveland, (2) Lakewood,in the county of Cuyahoga and State of Ohio, have invented a ,certainnew and useful Improvement in Rheostats, of which the following is afull, clear, and exact description, reference being had to the accomanying drawings.

T 1e aim of our invention is to improve, simplify, and cheapen theconstruction of rheostats of the ty e wherein the resistor element iscomposed) of carbon or like sub stance.

Two very desirable embodiments of our invention are illustrated in theaccompanying drawing wherein Fig. I1 shows one form of our improvedrheostat in side elevation and as mounted on a su porting member; Fig. 2

is a central longitu inal section through the same; Fi 3 is a front viewof the device shown in ig. 1, removed from the supporting member andwith the adjusting screw in section; Fig. 4 is a section on the line4--4 of Fig. 2; Fig. 5 is an elevational view of another form of ourinvention mounted on a su porting member; Fig. 6 is a central longitumal sectionon the line 6--6 of Fig. 5 looking in the direction of thearrows; and Fig. 7 1s a section on the line 7-7 of Fig. 6.

The supporting member 1 may be the instrument board of any ap aratuswherewith our invention is adapted or use.

The form of the invention illustrated in Figs. 1 to 4 comprises a tube 2of insulating material, such as fiber, and to the ends of the tube areapplied metal ferrules 3 and 4. These ferrules may be secured to' thetube in anyl suitable manner, as by the obvious expedients of s inningthem thereon, indenting the ferru es so as to interlock them with a partof the tube, or they may be secured b suitable fastening means, as brivets 5. t is essential, however, that they securely attached to thetube, and that they be spaced apart suiciently to insure effectiveinsulation of one from the other. A plate 6 closes the outer end of thetube 2 and is held in place by lugs 7 that extend from the end of theferrule 4 through slots in said plate and are turned over therebeyond.The plate is extended at one side where it is formed with an internallythreaded boss 8 for the reception of a terminal screw 9 by means of1922. Serial Fo. 558,125.

which an electrical conductor 10 may be attached to the plate.

A supporting plate 12 is similarly secured to the ofpposite end of thetube 2 by lugs 13 of the errule 3 that are projected through slots insaid plate 12 and turned over therebeyond. The supportin plate is shownas extended an appreciabe distance on opposite sides of the tube 2, andthe extended portions are provided with apertures through which screws14 pass by means of which the rheostat is secured to the support ingmember 1. One end of the supporting plate 12 is turned laterally whereit is provided with an internally threaded boss 15 for the rece tion ofa terminal screw 16 by means of w ich an electrical conductor 17 may beattached to said plate.

It will be seen from what has so far been described that the plates 6and 12 constitute the terminals of the rheostat, and that they areinsulated from eachother by the tube 2. These terminal plates areadapted to be electrically connected through a resistor element ofvariable conductivity which we shall now describe.

A series of carbon, preferably graphitic carbon, disks 20 are adapted tobe compresed with varying degrees of pressure between the plate 6 andapressure plate 21 as by means of an adjustin screw 22 that is threadedthrou h a thimle 23, applied to the supporting p ate 12, the inner endof the screw being tapered to fit within a correspondingly shapedepression in the center o the pressure plate 21. The outer end of thescrew 22 is equipped With a knob 24. The supporting member 1 has anaperture 25 for the aecommodation of the adjusting screw. 'lo preventundue separation of the several disks 20 and the pressure plate 21 whenthe adjusting screw is retracted, to open the circuit (in which case thedevice serves as a switch) and to revent their dislodgment from the tube2 1n the event that the supporting plate 12 is removed, a sleeve 26.preferably of insulating material, is pressed into the end of the tube 2`to form a shoulder -Wherewith the peripheral portion of the pressureplate 21 may engage.

The form of the invention illustrated in- Figs. 5, 6 and 7 is made up ofa sleeve 3() of suitable insulating materlal which, in this form of theinvention, may be fiber, glass, porcelain, or other suitable insulatingma- .contact with said member.

terial, and a sleeve 31 is fitted into one end of the tube to provide ashoulder. Between this shoulder and the opposite end of the tube reposethe carbon disks 32 engaged at each end by substantially identicalpressure plates 33 having central projections 34. The projection of thepressure plate 33 adjacent the sleeve 31 4tits within a recess in theend of an adjusting screw 35 which has a knob 36 applied to its outerend. The adjustmg screw is threaded through a supporting plate 37, shownin the present instance as circular, and secured to the supporting plate37 on opposite sides o the tube 30 are the outwardly turned ends of asubstantially U-shaped member 38 which has its central branch engagedacross the outer end of the tube 30 and perforated to receive theprojection 34 o the adjacent pressure plate 33. Screws 40 and 41 connectthe ends of the U-shaped member to the supporting plate 37, and thesescrews are insulated from the supporting plate, while being inelectrical The screws 40 and 41 have nuts 4Q applied to their threadedends, and the screw 40 is sufficiently long to receive a knurled nut 43so that a binding post is thus constituted of the.screw 40 to which anelectrical conductor 44 may be applied and clamped between the nut 43and the adjacent nut 42. Said conductor, therefore, is in electricalconnection with the pressure plate 33 at the outer end of the series ofcarbon disks 32, while the pressure plate at the opposite end of saidseries has electrical connection, through the adjusting screw 35, withthe supporting plate 37. The supporting plate 37 is spaced from thesupporting member 1 by a bar 48, that is interposed between the two andthrough the ends of which the screws 46 and 47 pass, to provideclearance for the heads of the former screws 40 and 41. The respectivescrews 46 and 47 have nuts 50 and 51 applied to their inner ends, andthe latter screw is made sufiiciently long to receive a knurled nut 52between which and the nut 51 the end of an electrical conductor 53 maybe clamped. The last mentioned conductor, therefore, has electricalconnection with the series of carbon disks through the screw 47,supportinF plate 37, adjusting screw 35, and the adjacent pressure plate33.

It will be readily understood from the foregoing description that ineach embodiment ot the invention current flowing from one of theelectrical conductors to the other may be varied by altering thepressure imposed upon the carbon disks by means of the adjusting screw,in accordance with the well known principle of carbon rheostats.

Having thus described our invention, what we claim is:

1. A rheostat of the character described comprising a tube of insulatingmaterial, an

element fastened to and closing each end of the tube, said elementsbeing of conductive material and insulated from each other by the tube,a pressure screw threaded throng one of the said elements, a pressureplate applied to the end of the screw, a series of carion disksinterposed between said pressure plate and the element which closes theopposite end of the tube, and means for connecting electrical conductorsto the aforesaid elements.

2. A rheostat of the character set' for' comprising a tube of insulatingmaterial, a sleeve pressed into one end of the tube thereby to provide ashoulder, an element of conductive material closing each end of thetube, said elements being insulated from each other by the tube, anadjusting screw threaded through one of the elements and projecting intothe tube, a pressure plate applied to the end of the screw,

said plate being limited in its outward movement by said shoulder, aseries of carbon disks interposed between said pressure plate and theelement situated at the other end of the tube, and means for connectingelectrical conductors to the aforesaid elements.

3. A rheostat of the character set forth comprising a tube of insulatinmaterial, a ferrule secured to each end o the tube, a

plate of conductive material applied to each end of the tube, eachfel-rule and the adjacent plate having interlocking parts whereby theplates are secured to the tube through the intervention of saidferrules, means for connecting electrical conductors to said plates, ascrew threaded through one of said plates and projecting into the tube,a pressure plate applied to the inner end of the screw, and a series ofcarbon disks interposed between said pressure plate and the platesituated at the opposite end of said tube.

4. A rheostat of the character set forth comprising a tube of insulatingmaterial, a ferrule fitting over and secured to` each end of the tube,said ferrules having lugs extending from their .outer ends, a plateapplied to each end of the tube, said plate having apertures throughwhich the lugs of the adjacent. ferrule extend and beyond which the lugsare turned over thereby to secure the plates to the tube, one of saidplates having a threaded hollow boss, a pressure screw threaded throughsaid boss and projecting centrally into the tube, a pressure platewithin the tube, said pressure plate and the inner end of the screwhaving part-s interengaging with each other, a series of carbon disksinterposed between the pressure plate and the plate situated at theopposite end of the tube, a sleeve fitted into the end of the tube intowhich the screw projects, the sleeve providing a shoulder against whichthe pressure plate may enage when the screw is retracted, and means orattaching electric 4kconductors tothe plates that are applied to theends of the sleeve. y

5. A rheostat of the character set forth comprising a tube of insulatingmaterial,

aplate secured to and closing one end of the tube, said plate having alateral extension,

means .for connecting an electrical conductor to said extension, a platesecured to and closing the opposite end of the tube, said plateextending in opposite directions beyond the tube thereby to providesupport ing ears, the plate extending beyond one of said supporting earsand turned laterally to form a lug, means for connecting an electricalconductor to said lug, a screw extending into the tube through the lastmentioned plate and having threaded connection therewith, a pressureplate applied to the inner end of the screw, and a series of carbondisks interposed between the pressure plate and the first mentionedplate.

6. In a rheostat of the character set forth, the combination of asupporting plate, a U-shaped member having its ends secured to andinsulated from diametrically opposed portions of the supporting plate, atube of insulating material reposing between the side branches of theU-shaped member and confined between the central ortion thereof and theopposed portion o the supporting plate, a variable pressure means.carried by t e supporting plate and extending into the tube, acompressible body -of resistance material within the tube and interposedbetween said means and the central portion of the U-shaped member, andmeans for connecting an electrical conductor to'eacli the U-shapedmember and the supporting plate.

7. In a rheostat of the character set forth, the combination of asupporting element, a U-shaped member having its ends connected to andinsulated from the supporting member, a tube of insulating materialreposing between the side branches of the U- shaped member and confinedbetween the supporting element and the central. portion of the U-shapedmember, said central portion having an aperture in axial alignment withthe bore of the tube, a screw threaded through the supportinglelementand projecting into the tube and aving a recess in its inner end that issubstantially in axial alignment with the bore of the tube, a series ofcarbon disks, a pressure late applied to each end of said series ofdisks, each pressure plate having a central projection, the projectionof one of said plates being engaged throu h the aperture in the centralportion of t e U-shaped member and the projection of the other engagedwithin the recess of the screw, and means for connecting an electricalconductor to each of the U-shaped member and the supporting element.

8. In a rheostat of the character set forth, the combination of asupporting element, a U-shaped member having its ends turned outwardly,screws connecting the ends of said member to diametrically opposedportions of the supporting element, means insulating the member from thesupporting element, one of said screws constituting a binding postthrough which a conductor is radapted to have electrical connection with,tor lis adapted to have electrical connection with the supportingelement, a tube of insulating material reposing between the sidebranches of the U-shaped member and confined between the central portionof said member and the supporting element, an ada justing screw threadedthrough the supporting element and projecting into the tube, and acompressible body of resistance material confined between the inner endof the screw and the central portion of the U-shaped member.

In testimony whereof, we hereunto alx our signatures.

JOHN C. BOYTON. HERBERT A. STEVENSON.

